How to Convert Bytes to Integers in Python Using int.from_bytes()?

Byte to Integer Conversion in Python

When working with encryption and decryption algorithms, it is often necessary to convert byte sequences to integer values and vice versa. In Python, the process of converting bytes to integers is straightforward using the built-in int.from_bytes() function.

The int.from_bytes() function takes three arguments: bytes, byteorder, and signed (optional). The bytes argument specifies the byte sequence to convert, byteorder indicates the byte order (either "big" or "little"), and signed determines if the value should be treated as a signed integer or not (default is False).

For example, to convert a byte sequence b'x03' to an integer, we can use:

<code class="python">bytes([3]) == b'\x03'
result = int.from_bytes(b'\x03', byteorder='big')
print(result)  # 3</code>

In this case, the byteorder='big' argument indicates that the most significant byte should be at the beginning of the byte sequence. If we used byteorder='little', the same byte sequence would be interpreted as 256 instead.

The signed argument can be used to specify if the value should be treated as a signed integer. For example, to convert a sequence b'xfcx00' to a signed integer, we can use:

<code class="python">result = int.from_bytes(b'\xfc\x00', byteorder='big', signed=True)
print(result)  # -1024</code>

This will interpret the sequence as a signed integer using two's complement encoding, resulting in a value of -1024.

Overall, the int.from_bytes() function provides a simple and efficient way to convert byte sequences to integer values in Python. By specifying the byte order and signedness, you can ensure that the conversion is performed as expected.

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